Following the events of Ragnarok, the vast majority of those humans who managed to make it across the Bifrost, stayed in Asgard. The land, being large for so few Aesir, could easily accommodate those humans who wanted to stay. Three human Kingdoms arose upon the lands of Asgard; Idavol, Vangr and Dalir, with three powerful human Kings chosen by the Aesir to rule these lands. For a while, there was peace and trade and prosperity.
Northmen wil be Northmen however, and the son of King Elric Ubbarson, Alfric Elfricson was a bloodthirsty warrior, who did not like peace, or trade, but prosperity; prosperity he cherished - his own.
Alfric was just a child when Ragnarok hit; a child who had been out in the wilds with friends when the war came to town. When Freya had ridden to marshal their town to flee, the Kings son Alfric had been missing; last seen heading for the woods earlier that day. And it was Freya who had found him; the boy was wide-eyed, staring and almost insensible, sat at the base of a tree with his friends torn to shred around him. Freya had scooped him up and deposited him with his father before riding off.
As Alfric grew his thirst for blood grew with him, and raising a war band he went a'Viking on the other two human Kingdoms. At first this was not commented on or given much notice at all; this is what Northmen did, and all knew their would be raiding in return in due time. But Alfric got savage, and cruel; taking more than a raiders share, and burning what was left. All along the coasts of Idavol and Vangr towns and villages were left in ash.
Complaints were made to King Elfric, and eventually the King had to take action against his son. But he never got to; the night before the trial was planned for Alfric's deeds, the King was murdered in his bed..... and Alfric became King.